For various cryogenic purposes and other uses in which a deep-cooled liquid, e.g. a liquefied gas, must be transported from one location to another, it is a common practice to provide a multi-path duct system designed to protect the deep-cooled liquid from environmental temperatures, i.e. to limit the cold losses between an upstream location and a downstream location and hence prevent the incursion of heat to the deep-cooled medium.
Such systems may be used, for example, for the delivery of liquefied natural gas from a storage vessel or liquefaction plant to a consumer, e.g. a regasification plant or a transport vessel or the like. They may also have application in the deep-cooling of articles which are to be embrittled prior to or during comminution. For instance, it is becoming increasingly advantageous to comminute used automotive vehicle tires, rubber scraps and synthetic-resin materials such as thermoplastic foils by low-temperature milling, i.e. by subjecting the articles to chilling with a low-temperature fluid, i.e. a deep-cooled liquid, and the fluid can be transported thereto by a duct system of the type under discussion from a storage tank, cryostat or other low-temperature generator (e.g. a refrigerating unit).
Still other applications will be immediately apparent. For example, various electrical apparatuses operate more effectively at cryogenic temperatures, e.g. superconductive magnets and like devices used in particle accelerators. For the cooling of the magnetic distribution systems for low-temperature fluids, liquefied gases are usually necessary.
With all of these systems, it is important to provide a means for connecting two parts of the duct system and, since the duct system itself is generally rather complex, correspondingly complex coupling or connector arrangements have been proposed heretofore or must be fabricated on the spot.
For example, the duct systems which have been employed heretofore for the transport of a deep-cooled medium between the source and the consumer have comprised multi-path pipe arrangements using coaxial ducts to define the various flow passages and, generally, vacuum chambers which are intended to limit the incursion of heat into the systems or the loss of cold therefrom.
In conventional systems of this type, various structural and operational problems have arisen. For example, when the system was traversed by the deep-cooled medium (liquefied gas) mechanical stresses arose which affected operation of the systems. Furthermore, the cold losses at any junction or connector were significant. Finally, the construction of the connector has invariably been complicated and the sealing of the various flow passages from one another, so as to avoid heat penetration into the interior, has not been fully satisfactory. A disadvantage which, although mentioned last, is perhaps the most significant, in conventional connector arrangements for duct systems of the character described is that such systems do not permit of relative mobility of the parts of duct systems which were to be connected, either during assembly or because of thermal expansion and contraction considerations. As a result high precision in assembly and construction was required with consequent high labor and fabrication costs.